The present invention relates to an ATM (asynchronous transfer mode) network system and more particularly to PVC and SVC resource management in an ATM network, a method for connection admission control, and a system configuration.
In this specification, the following abbreviations are used.PVC: Permanent virtual connection
SVC: Switched virtual connection PA1 VPC: Virtual path connection PA1 VCC: Virtual channel connection PA1 PVPC: Permanent virtual path connection PA1 PVCC: Permanent virtual channel connection PA1 SVCC: Switched virtual channel connection PA1 ITU-T (International Telecommunication Union--Telecommunication Standardization Sector) Recommendation I.732 PA1 (1) The SVC is set by sending and receiving messages between the network equipment 200 and the terminal equipment or another network equipment and it is not necessary to send and receive messages between the network equipment 200 and the network management equipment. Therefore, this request condition is satisfied. PA1 (2) For PVC setup, a setup request is issued to the network management equipment first. Thereafter, the network management equipment sends the setup request to the network equipment 200 and the network equipment 200 executes connection admission control. The network management equipment obtains the result, updates the resource management data in the network management equipment, and then instructs PVC setup to the network equipment 200. Therefore, it is necessary to send and receive a message two times between the network management equipment and the network equipment 200. PA1 (3) Since the common connection admission control 804 is applied to PVC and SVC, the resource allocation can be executed without considering the classification of PVC and SVC. PA1 (4) Since the common connection admission control 804 is applied to PVC and SVC, the resource allocation can be executed without considering the classification of PVC and SVC. However, on the other hand, for example, it is difficult to perform an individual process such as counting call blocking for SVC but not counting call blocking for PVC.
"Functional characteristics of ATM equipment" (hereinafter expressed by Draft I. 732) specifies the function model of the ATM network equipment (ATM exchange or ATM crossconnect). According to the Draft I. 732 mentioned above, the connection admission control function for setting the VPC or VCC is arranged in the ATM network equipment.
FIG. 14 shows a function model for connection admission control in an ATM network equipment 200 extracted from FIG. 6.1 of the Draft I. 732.
The network equipment 200 has a signaling application 800 for controlling SVC connected to a terminal equipment or another network equipment, a message communications function 802 for communicating with a network management equipment for controlling PVC, and an equipment management function 801 for controlling the operation of the equipment on the basis of a message received by the message communications function 802, and the signaling application 800 has a routing table 803 for routing SVC, and the equipment management function 801 has a routing table 804 for routing PVC.
The SVC control and PVC control are executed via an application program and a function program which are different between the controls, so that a coordination function 803 is provided in the network equipment 200 so as to coordinate these controls. The coordination function 803 has a connection admission control 804 for executing the connection admission control for PVC and SVC at the same time and the connection admission control 804 comprises an admission control algorithm 805 shared by PVC and SVC, an identifier management table 806, and a bandwidth management table 807.
However, when PVC and SVC which are different in the setup method from each other are controlled in the coexisting state, the following conditions (1) to (4) are required. A term of "resource" in the following explanation in this specification indicates, for example, an identifier (VPI and VCI) and a bandwidth.
(1) The SVC setup delay time should be satisfied.
For SVC, the setup delay time is specified and it is necessary to complete setup within several hundreds ms. The network management equipment and network equipment are generally connected via a wide area network and the required communication time between them is long. Therefore, the resource management system in which the network management equipment and network equipment send and receive messages between them every connection setup cannot satisfy this request condition.
(2) The communication overhead during PVC setup should be reduced.
For PVC, the aforementioned setup delay time specified for SVC is not specified. However, for connection setup, it is desirable to reduce the communication count or the communication data amount between the network management equipment and the network equipment. The reason is that the required communication time between the network management equipment and the network equipment is long in the same way as with (1) mentioned above.
(3) The PVC and SVC can coexist in the same low-order layer.
For example, to make PVCC and SVCC coexist in the same VPC, it is necessary to allocate resources in the same VPC to a plurality of connections which are different from each other in the setup method.
(4) The call blocking of SVC setup can be counted.
When resources are insufficient during connection admission control, SVC becomes call blocking but PVC is free of call blocking. Therefore, in SVC, the resource allocation by network designing is not changed immediately at the point of time when call blocking occurs but the resource allocation is changed at the point of time when the call blocking rate (call blocking count per hour) becomes worse than a certain threshold value. On the other hand, in PVC, when connections cannot be admitted due to insufficient resources during connection admission control, the PVC resource allocation is changed immediately by network designing.
According to the conventional resource management model shown in the aforementioned Draft I. 732, as shown in FIG. 14, the connection admission control function which is one of the resource managements is arranged in the network equipment 200 and the connection admission control function is used for both PVC setup and SVC setup. When the aforementioned request conditions (1) to (4) are examined in this constitution, the following results are obtained.
According to the conventional resource management system as mentioned above, for the request condition (2) of reduction of the communication overhead between the network management equipment and the network equipment during PVC setup, a problem arises that it is necessary to send and receive a message two times. For the request condition (4) of counting SVC call blocking, the network equipment executes the connection admission control without considering the classification of PVC and SVC, so that it is difficult to count call blocking only of SVC.